removing filament always jams extruder (Anycubic Mega-S)

[686 Shooter]

On my Mega S the bowden tube was not tight against the nozzle. This will contribute to your problem. Also the tube itself is not of great quality, I replaced mine with some Capricorn tubing.

To ensure your bowden tube is tightly sealed against the heat break heat the hot end to 200 degrees, loosen the tube fitting on the top of the hot end by 3/4 to 1 turn. Push the tube in until you are sure the tube is touching the heat break then tighten the fitting. This will give you a nice compressed seal and avoid any leaks. This solved the problem for me.

I also found that it helped to push the filament into the hot end until you get some coming out then quickly pull the filament back.